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In the first place, a tree generates another tree according to a known natural law. But the tree produced is of the same genus; and so it produces itself generically. On the one hand, as effect it is continually self-produced; on the other hand, as cause it continually produces itself, and so perpetuates itself generically.
Secondly, a tree produces itself as an individual. This kind of effect no doubt we call growth; but it is quite different from any increase according to mechanical laws, and is to be reckoned as generation, though under another name. The matter that the tree incorporates it previously works up into a specifically peculiar quality, which natural mechanism external to it cannot supply; and thus it develops itself by aid of a material which, as compounded, is its own product. No doubt, as regards the constituents got from nature without, it must only be regarded as an educt; but yet in the separation and recombination of this raw material we see such an originality in the separating and formative faculty of this kind of natural being, as is infinitely beyond the reach of art, if the attempt is made to reconstruct such vegetable products out of elements obtained by275 their dissection or material supplied by nature for their sustenance.
Thirdly, each part of a tree generates itself in such a way that the maintenance of any one part depends reciprocally on the maintenance of the rest. A bud of one tree engrafted on the twig of another produces in the alien stock a plant of its own kind, and so also a scion engrafted on a foreign stem. Hence we may regard each twig or leaf of the same tree as merely engrafted or inoculated into it, and so as an independent tree attached to another and parasitically nourished by it. At the same time, while the leaves are products of the tree they also in turn give support to it; for the repeated defoliation of a tree kills it, and its growth thus depends on the action of the leaves upon the stem. The self-help of nature in case of injury in the vegetable creation, when the want of a part that is necessary for the maintenance of its neighbours is supplied by the remaining parts; and the abortions or malformations in growth, in which certain parts, on account of casual defects or hindrances, form themselves in a new way to maintain what exists, and so produce an anomalous creature, I shall only mention in passing, though they are among the most wonderful properties of organised creatures.
According to the character alleged in the preceding section, a thing, which, though a natural product, is to be cognised as only possible as a natural purpose, must bear itself alternately as cause and as effect. This, however, is a somewhat inexact and276 indeterminate expression which needs derivation from a determinate concept.
Causal combination as thought merely by the Understanding is a connexion constituting an ever-progressive series (of causes and effects); and things which as effects presuppose others as causes cannot be reciprocally at the same time causes of these. This sort of causal combination we call that of effective causes (nexus effectivus). But on the other hand, a causal combination according to a concept of Reason (of purposes) can also be thought, which regarded as a series would lead either forwards or backwards; in this the thing that has been called the effect may with equal propriety be termed the cause of that of which it is the effect. In the practical department of human art we easily find connexions such as this; e.g. a house, no doubt, is the cause of the money received for rent, but also conversely the representation of this possible income was the cause of building the house. Such a causal connexion we call that of final causes (nexus finalis). We may perhaps suitably name the first the connexion of real causes, the second of those which are ideal; because from this nomenclature it is at once comprehended that there can be no more than these two kinds of causality.
For a thing to be a natural purpose in the first place it is requisite that its parts (as regards their being and their form) are only possible through their reference to the whole. For the thing itself is a purpose and so is comprehended under a concept or an Idea which must determine a priori all that is to be contained in it. But so far as a thing is only thought as possible in this way, it is a mere work of art; i.e. a product of one rational cause277 distinct from the matter (of the parts), whose causality (in the collection and combination of the parts) is determined through its Idea of a whole possible by their means (and consequently not through external nature).
But if a thing as a natural product is to involve in itself and in its internal possibility a reference to purposes,—i.e. to be possible only as a natural purpose, and without the causality of the concepts of rational beings external to itself,—then it is requisite secondly that its parts should so combine in the unity of a whole that they are reciprocally cause and effect of each other's form. Only in this way can the Idea of the whole conversely (reciprocally) determine the form and combination of all the parts; not indeed as cause—for then it would be an artificial product—but as the ground of cognition, for him who is judging it, of the systematic unity and combination of all the manifold contained in the given material.
For a body then which is to be judged in itself and its internal possibility as a natural purpose, it is requisite that its parts mutually depend upon each other both as to their form and their combination, and so produce a whole by their own causality; while conversely the concept of the whole may be regarded as its cause according to a principle (in a being possessing a causality according to concepts adequate to such a product). In this case then the connexion of effective causes may be judged as an effect through final causes.
In such a product of nature every part not only exists by means of the other parts, but is thought as existing for the sake of the others and the whole, that is as an (organic) instrument. Thus, however, it might be an artificial instrument, and so might be278 represented only as a purpose that is possible in general; but also its parts are all organs reciprocally producing each other. This can never be the case with artificial instruments, but only with nature which supplies all the material for instruments (even for those of art). Only a product of such a kind can be called a natural purpose, and this because it is an organised and self-organising being.
In a watch one part is the instrument for moving the other parts, but the wheel is not the effective cause of the production of the others; no doubt one part is for the sake of the others, but it does not exist by their means. In this case the producing cause of the parts and of their form is not contained in the nature (of the material), but is external to it in a being which can produce effects according to Ideas of a whole possible by means of its causality. Hence a watch wheel does not produce other wheels, still less does one watch produce other watches, utilising (organising) foreign material for that purpose; hence it does not replace of itself parts of which it has been deprived, nor does it make good what is lacking in a first formation by the addition of the missing parts, nor if it has gone out of order does it repair itself—all of which, on the contrary, we may expect from organised nature.—An organised being is then not a mere machine, for that has merely moving power, but it possesses in itself formative power of a self-propagating kind which it communicates to its materials though they have it not of themselves; it organises them, in fact, and this cannot be explained by the mere mechanical faculty of motion.
